The following co-assigned patents/patent applications are related to the present invention and are hereby incorporated herein by reference:
This invention relates generally to semiconductor device fabrication and more specifically to the formation of a TiN-based film.
Films containing titanium nitride are commonly used as a diffusion barrier in contacts, vias, trenches, and interconnect stacks. They are also used as a xe2x80x9cgluexe2x80x9d layer for chemical vapor deposited (CVD) tungsten, as a nucleation layer for CVD tungsten and CVD aluminum, as a liner for contacts, vias and trenches, as a capacitor electrode, and as an anti-reflective coating. A good barrier layer should have: good step coverage to achieve void-free plug formation and adequate barrier thickness at the bottom of the contact/via/trench; good diffusion barrier properties to prevent diffusion of metals and other materials into underlying layers; inertness and low reactivity with adjacent materials during thermal cycles; and acceptable electrical properties such as low resistivity, low contact/via resistance and low junction leakage.
Currently, TiN-based barrier films are formed by physical vapor deposition (PVD) using reactive sputtering. This type of sputtering method is line-of-sight technique and produces films with poor step coverage. As minimum feature sizes continues to shrink and the aspect ratio of contacts/vias/trenches continues to increase, processes that produce conformal films are in great demand.
CVD processes offer the potential advantage of good step coverage and have attracted increasing attention in the past few years for fabricating TiN based films. Two types of CVD processes are being developed currently: one based on metal-organic (MO) precursors, such as tetras(dimethylamino)-titanium (TDMAT) and tetras(diethylamino)-titanium (TDEAT); and the other based on inorganic precursors, such as TiCl4/NH3. The MO based processes produce films with high carbon content and low stability. The TiCl4/NH3 process requires high deposition temperature and have severe problems associated with NH4Cl salt formation.
Prior CVD process for TiSixNy uses Ti[N(C2H5)2]4/NH3/SiH4 chemistry. The drawbacks of this approach includes: gas phase reaction between the Ti precursor and NH3, lower density, less stable films than those using TiCl4 as a precursor, and lower vapor pressure of metalorganic precursor as compared to TiCl4.
A process for depositing a TiN film on tools was developed using CVD. See F. H. M. Sanders and G. Verspui, Influence of Temperature on the Growth of TiN Films by Plasma-Assisted Chemical Vapor Deposition, 161 THIN SOLD FILMS L87-L90 (1988). This method uses a combination of H2, N2, and TiCl4 in conjunction with a plasma to form the TiN layer on the tool to prevent corrosion of the tool.
The instant invention relates to the deposition of titanium nitride based films for barrier layers, gate dielectrics, and for capacitor electrodes. Advantages of the instant inventions include: better step coverage than standard PVD formed TiN based films; use of TiCl4 in the deposition of the filmxe2x80x94TiCl4 has higher vapor pressure and is less expensive than MO precursors; higher purity, density, and stability of the films formed by the instant invention than MOCVD formed films; greatly reduced formation of NH4Cl salts; lower deposition temperature than standard processes; and flexibility in control of Si/N and B/N atomic ratios.
An embodiment of the instant invention is a method of depositing a TiN-based film over a semiconductor wafer, the method comprising the steps of: substantially simultaneously subjecting the semiconductor wafer to TiCl4, H2, and N2; and subjecting the semiconductor wafer to a plasma, such that the combination of the TiCl4, H2, and N2 and the plasma cause the deposition of a TiN based film to form over the semiconductor wafer. Another embodiment of the instant invention involves additionally subjecting the semiconductor wafer to SiH4 so as to form a TiSixNy film over the semiconductor wafer. Another embodiment of the instant invention involves additionally subjecting the semiconductor wafer to B2H6 so as to form a TiNxBy layer over the semiconductor wafer.